Field of the Invention
Embodiments of the invention generally relate to a filter module configured for exhaust applications, and a method and apparatus for testing the same.
Description of the Related Art
In many cleanroom and contaminant applications, filter modules are often utilized in an exhaust configuration to remove air or other fluids from rooms or equipment. In many of these applications, regulations, certifications and/or process protocols require that the filter be tested for overall efficiency after installation into the module. However, testing a filter module in this manner is a difficult challenge. Particularly, the interstitial space defined between the housing and the filter disposed therein often cannot be readily accessed by a technician. Thus, downstream sampling of the installed exhaust filter often cannot be performed. Additionally, sampling within the interstitial space defined between the housing of the module and the filter may not be accurate due to poor mixing of air within the filter housing. Thus, testing of an installed exhaust filter is usually performed in the reverse flow direction to facilitate downstream sampling from the cleanroom side of the filter. This manner of testing is controversial, as many believe that some pinhole filter leaks are flow direction dependent, and as such, a filter passing an efficiency test with air flowing in a first direction, may fail when the flow through the filter is reversed to the direction used during operation of the filter of the cleanroom. As leaking filters may pose health hazards, allow downstream contamination and present regulatory issues or other undesirable problems, it is highly desirable to test filters in the same flow direction utilized during normal filter operation.
Thus, there is a need for a method and apparatus for efficiency testing of a filter installed in an exhaust housing.